Spark plug



May 27 I924.

' J. s. COYLE SPARK PLUG Orig inal Fil ed Nov. 17, 1920 w ATTORIVE Patented May 27, 1924.

JAMES STEPHEN COYLE, OF ST. LOUIS, MISSOURI.

SPARK PLUG.

continuation of application Serial No. 424,657, filed November 17, 1920. This application filed November 28, 1923. Serial No. 677,568.

To all whom it may concern:

Be it known that '1, JAMES STEPHEN COYLE, a citizen of the United States, and residing at St. Louis, State of Missouri, have invented the new and useful Improvement in Spark Plugs, of which the following is a specification.

he presentinvention relates to new and useful improvements in ignition devices for internal combustion motors, and it pertains more particularly to spark plugs therefor. This application is a continuation of application Serial Number 424557, filed November 17, 1920.

It is one of the primary objects of the invention to provide a spark plug in which the electrodes, and more particularly the core or jacket for the central electrode, will be kept free from carbon and oil in order to prevent short-circuiting of the electric current within the spark plug shell.

Another object of the invention is to provide a spark plug having means adapted to utilize the heat generated by the explosive charge in the cylinder for the purpose of burning the oil and carbon in order to prevent deposit of carbon,

It is still a further object of the invention to so construct a spark plugthat the heat of the explosion of the combustible charge will be presented directly to the porcelain core in order that it may carryout the aforementioned operation of burning the oil and keeping the carbon deposits off the porcelain core.

Further objects will appear from the detail description, taken in connection with the accompanying drawing, in which:

Figure 1 is a longitudinal sectional view of aspark plug constructed in accordance with the present invention; and

Figure 2 is a bottom plan view thereof.

Referring to the accompanying drawings, the reference character 5 designates the shell of the plug, and 6 designates the porcelain core or jacket, The shell 5 is provided on its lower end with an electrode or terminal 7, and extending centrally and longitudinally of the porcelain core 6 and projecting from the end thereof is an electrode 8. The porcelain core is provided with washers 9 'by means of which a gas-tight jointvis formed between the shell 5 and the nut 10 by means of which the porcelain core is secured within the shell.

jecting from the lower end of the porcelain core 6 and lying within the end of the shell 5, is a tubular member 13, and said tubular member is preferably formed of metal. This metallic tube 13 surrounds the major .portion of the central electrode 8 and fits tightly the lower end of the porcelain core 6. In order to secure the metallic tube 13 in position upon the lower end of the porcelain core 6, it is bent or c'rimped inwardly at. the circumferential groove 12 as designated by the reference character l l.

It will be seen that the metallic tube 13 envelops the'electrode 8 and as shown it also envelops the end of the core 6. As-shownv the tube extends to the end of the shell or slightly therebeyond so as to be enveloped by the shell. Upon ignition of the explosive charge, a part of the heat of the incandescent gases will be absorbed by the metallic tube, and since it is thermally insulated from the metallicshell of the spark plug, and, therefore, from the metallic engine cylinder, this tube will become hot, and in fact incandescent. Accordingly any oil or carbon which may have become deposited thereon will be burned off. Moreover the incandescent tube will by radiation direct its heat on the center electrode, the end of the porcelain core and-even on the inner walls of the shell so as to burn the carbon therefrom. As a matter of fact during actual operation the deposit of oil and carbonis prevented. In the usual spark plug, the oil colic ts, during the intake stroke, as a film on the electrodes and core and also on the shell, and during the ignition stroke this film is not completely vaporized but its residue becomes baked on these parts; during each. cycle this layer .of residue builds up until it forms a conducting bridge between the electrodes. In accordance with this invention, however, the provision of the extended. metallic tube, thermally insulated, provides an incansorbed by the tube during the ignition stroke cannot leak oft tothe engine, but must be dissipated in breaking up the oil. Furthermore any oil film deposited on the electrodes or core will be subject to the radiation of heat from the incandescent tube so as to become completely vaporized. Furthermore a zone of intense heat is created within the tube so that any oil entering this zone will become completely vaporized. AC1

cordingly all deposit ot carbon is completely prevented.

It will be seen that the metallic tube is an extended one so as to providean extended hot wall between the central electrode and the shell. While this tube extends as shown, slightly beyond the shell, itdoes not form one of the electrodes, but the electrodes 7 and 8 form a spark gap therebeyond. vVhile in the illustrated embodiment the metallic tube 13 is shown as forced into a circumferential groove 11 to retain it in place, it is to be understood that any suitable manner of securing the same may be resorted to without departing from the spirit of the invention. It is further obvious that various changes may be made in detailsof construction without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited is claimed is 1. A spark plug comprising, a shell, a core therein having an electrode, and a metallic tube on said core, enveloping said electrode and enveloped by said shell, adapted to form a hot wall between said electrode and said shell in order to prevent the deposit of carbon.

Aspark plug comprising, a shell, a core therein having an electrode, and a metallic tube enveloping the end of said core within said shell and projecting therefrom adapted to form a hot wall enveloping said electrode in order to prevent the deposit of carbon.

4. A-spark plug comprising, a shell having an electrode, a core therein having an electrode cooperating with said shell electrode, and a metallic tube projecting from the end of said core between same and said shell and adapted to form a hot Wall enveloping said core electrode in order to prevent deposit of carbon.

5. A spark plug comprising, a shell, a core therein having an electrode, and a metallic tube mounted exteriorly of and "projecting from the end of said core within said shell out of sparking relation with said electrode and adapted to form an extended hot wall enveloping said electrode in order to prevent the deposit of carbon. 7 In testimony whereof I aiiix my signature this 26th day of November, 1923.

JAMES STEPHEN (DOYLE. 

